The present invention relates to portable power planers and in particular to an improved elevation adjusting arrangement for a power planer. In general, portable power planers comprise a motor driven rotary cutter head having one or more cutting blade assemblies disposed thereon for performing a cutting operation upon the surface of a workpiece as the cutter head rotates. The bottom surface of the tool comprises a fixed shoe located rearwardly of the cutter head and an adjustable shoe disposed forwardly of the cutter head. As the front shoe is adjusted upwardly or downwardly, the cutting depth of the cutting blade of the planer is adjusted accordingly.
Known elevation adjustment arrangements for power planers typically comprise a stud which extends upwardly from the front shoe through a boss having an adjustment cap threaded onto the top of the stud to move the shoe vertically upwardly or downwardly as the cap is turned. In general, however, no calibration is provided to indicate to the operator exactly and precisely the depth of cut setting. Also, fine adjustments generally cannot be made with conventional adjustment mechanisms.
Accordingly, it is one object of the present invention to provide an improved elevation adjusting arrangement for a power planer which includes an accurate and easily calibrated scale. Zero on the scale corresponds to the position of the adjustable shoe providing a zero depth of cut. The preferred embodiment of the present invention enables the operator to adjust the depth of the cut in 0.1 mm steps from 0 to 1.5 mm.
Another object of the present invention is to provide an improved elevation adjusting mechanism for a power planer which is highly stable and thus capable of accurate, fine adjustments in the depth of cut for more accuracy in cutting. The present invention accomplishes this by utilizing a double thread on a bolt engaging the stem of the adjustable shoe which permits the use of a steeper pitched thread to provide the desired range of elevational movement in the adjustable shoe with reduced rotational movement of the adjustment knob, while at the same time providing increased thread contact for improved stability.
Another object of the present invention is to provide an improved elevation adjusting mechanism having a positive "park" position wherein the adjustable shoe extends downwardly beyond the cutting blade of the cutting head so that the cutting blade does not mar the work surface when the power planer is set down. Additionally, the present invention also includes means for positively locating the park position.
Briefly, the preferred depth of cut adjustment mechanism for a power planer disclosed herein includes a double threaded bolt which extends downwardly into engagement with a corresponding internally double threaded stem extending upwardly from the front shoe of the planer. Rotation of the bolt is controlled by a knob attached to the head portion of the bolt. The knob in turn has associated therewith a height adjustment scale which is capable of being readily calibrated, wherein zero on the scale corresponds to the position of the adjustable front shoe providing zero depth of cut. The adjustment mechanism further provides a positively engageable park position wherein the front shoe is extended downwardly beyond the fixed shoe so that the cutting blade of the planer does not mar a smooth surface when the power planer is set to rest thereupon.
Other objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which: